docs: def _process_pathway_pubmed(self, limit):
          """
          Indicate that a pathway is annotated directly to a paper (is about)
              via it's pubmed id.
          :param limit:
          :return:
          """
          LOG.info("Processing KEGG pathways to pubmed ids")
          if self.test_mode:
              graph = self.testgraph
          else:
              graph = self.graph
          line_counter = 0
          raw = '/'.join((self.rawdir, self.files['pathway_pubmed']['file']))
          with open(raw, 'r', encoding="iso-8859-1") as csvfile:
              filereader = csv.reader(csvfile, delimiter='\t', quotechar='\"')
              for row in filereader:
                  line_counter += 1
                  (pubmed_id, kegg_pathway_num) = row
  
                  if self.test_mode and kegg_pathway_num not in self.test_ids['pathway']:
                      continue
  
                  pubmed_id = pubmed_id.upper()
                  # will look like KEGG-path:map04130
                  kegg_id = 'KEGG-' + kegg_pathway_num
  
                  r = Reference(graph, pubmed_id, self.globaltt['journal article'])
                  r.addRefToGraph()
                  graph.addTriple(pubmed_id, self.globaltt['is_about'], kegg_id)
  
                  if not self.test_mode and limit is not None and line_counter > limit:
                      break
  
          return